1. Field of the Invention
This invention has relation to baskets or other containers which are rotated so that many relatively small workpieces inside are tumbled over and over during processing, and particularly to apparatus which automatically positively positions a cover on such a rotatable container, maintains it in position against the force of the weight of the workpieces being tumbled, and automatically separates the cover from the container after the workpieces have been processed so that the container can be automatically removed and replaced with a container loaded with unprocessed workpieces.
2. Description of the Prior Art
It is known to manually fasten rotatable basket covers in place using various combinations of nuts and bolts or the like. Such methods positively hold the cover in place against the weight of workpieces being processed; but have the disadvantage that an attendant must be on hand to fasten and unfasten the cover. This takes time that is lost "down time" as far as operation of the processing equipment is concerned. Also, the point where this manual fastening and unfastening of the cover is done must be a point accessible to such attendant. This can be grossly inefficient as concerns layout of the processing line.
It is known to automatically or manually move a cover into place on such a rotatable basket using an overcenter spring action with reliance on the strength of the spring to hold the cover in place on the rotatable basket against weight of the workpieces. The disadvantages of the manual operation of such an apparatus are as set out above. Additionally, the weight of the workpieces which can be processed in such a basket is limited by the strength of the spring holding the cover in place. As the strength of the spring is increased, the difficulty in snapping the cover between its open and closed conditions is increased, and more time and/or force is required to accomplish this movement either manually or automatically.
When loading workpieces into a basket, it is not practical to anticipate the load size which will cause such a spring loaded cover to open. Overloading results in release of the tumbling workpieces into the processing equipment. This causes, at least, considerable down time to retrieve the workpieces and, all too often, damage to the processing equipment, contammination and/or loss of any processing fluids, and/or destruction or damage to the workpieces.
What was needed before the present invention was an apparatus which would automatically and positively move a basket cover from its open position in spaced relation to a rotatable basket to its closed position in positive contact with the basket as soon as the basket was positioned inside of a rotatable carrier; and which would automatically move such cover from its positive closed position to an open position as soon as the workpiece processing sequence has been completed, and the carrier had come to rest.